InsP3-induced Ca2+ release in dorsal root ganglion neurones.

The intracellular calcium signalling was studied on subpopulation of freshly isolated adult mouse dorsal root ganglia (DRG) neurones with large somatas (30-45 microns in diameter). The cytoplasmic Ca2+ concentration ([Ca2+]i) was measured using indo-1 based microfluorimetry. The extracellular application of ATP (100 microM) triggered both inward current and [Ca2+]i elevation. Removal of extracellular Ca2+ had no effect on both ATP-induced current and [Ca2+]i transient. The ATP-induced Ca2+ elevation was inhibited by intracellular perfusion of DRG neurones with 20 microM heparin, or by cells incubation with thapsigargin or ryanodine. We conclude that mouse proprioceptive sensory neurones are endowed with Ca2+-impermeable ionotropic P2X purinoreceptors and metabotropic P2Y purinoreceptors, which, by means of phospholipase C-driven inositol-trisphosphate (InsP3) production, trigger the InsP3-induced Ca2+ release from intracellular stores.